<VV> Thermister Swap?

[MarK Durham]

Jim is exactly right. It would be accurate at one point, and less accurate
progressively along the scale going up or down from that point. That is why
I said on the EFI, it took an approximate reading to fool the computer in
switching to normal temp mode form cold start mode and a resistor did that.
The computer only needed to see an approximate value within a range.

A guage needs to be more accurate than that.

Guys, its this type of thing that is happening to our aging cars that
prompted me to suggest installing a new movement in the dash to replace the
old one, (and you keep the original look) and to install a matching new
thermistor in the engine, so you have correct reading gauges. If its CHT,
VDO makes a 90 degree sweep guage that could be a direct replacement with a
VDO probe. Then your CHT would be good for longer than most of us would
have the cars! VDO also does transmission temp or oil temp gauges.
Regards



Mark Durham
Hauser, Idaho
62 Monza coupe Red/Red 4 speed


On Fri, Sep 5, 2014 at 12:32 PM, Jim Simpson via VirtualVairs <
virtualvairs at corvair.org> wrote:

> The short answer is no, it won't work.  The longer answer is that yes, you
> can put a suitable resistor in series with the Rochester thermistor and get
> a correct reading at one (1) temperature.  Pick the temperature you want to
> be "accurate" and you could find a resistor that would give you that one
> reading.
>
> The problem is that the Rochester and GM thermistors have different
> temperature vs resistance curves.  Even with the addition of a resistor,
> the curves will not overlay.   All you can do is make them cross each other
> at some point.
>
> If you want to use the Rochester thermistor, you will have to make (or have
> made) a black box to translate from it's response curve to the gauge
> response curve.  In principle, not a hard thing to do.  But it would take a
> little time and tinkering.
>
> I've been thinking about it a little and may give it a try in my spare time
> in order to refresh my electronics skills.  But don't hold your breath
> waiting for me to get it done...
>
> Jim Simpson
> Group Corvair
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